(672c) A Novel Ionic Liquid Pretreatment Strategy to Achieve Enhanced Cellulose Saccharification Kinetics

Biomass has the potential to be converted into value added products through a sugar platform. Sugar feedstock can also be converted to ethanol for fuel production. Techno-economic analysis conducted by NREL indicates that efficiency of the biomass saccharification step ? hydrolysis of cellulose to glucose - is critically important in making the process cost-competitive. Cellulose hydrolysis in aqueous media suffers from slow reaction rates and low yields because cellulose is a water-insoluble crystalline biopolymer. To accomplish its hydrolysis, the hydrolyzing enzymes (cellulases) and water have to penetrate the crystalline fibrils. The tight packing arrangement of the fibrils not only excludes the enzymes but also water. Pretreatment methods which increase the surface area accessible to water and cellulases are vital to improving the hydrolysis kinetics and conversion of cellulose to glucose. We developed a novel technique wherein the cellulose is dissolved in an ionic liquid (IL) and is subsequently regenerated as an amorphous precipitate by rapidly quenching the solution with an anti-solvent. Hydrolysis kinetics of the regenerated cellulose were significantly enhanced as measured by initial rate of reducing sugar formation. With an appropriate selection of enzymes, initial rates were approximately an order of magnitude greater than those of untreated cellulose. Because of their extremely low volatility, ionic liquids are expected to have minimal environmental impact. A unique solvency characteristic of ILs which makes them ideal to work is that they are able to instantly reject all the dissolved cellulose in presence of anti-solvents such as water, methanol and ethanol. Once the cellulose is precipitated, the anti-solvent used for displacement can easily be stripped off the non-volatile IL via flash distillation and the IL recovered for subsequent reuse.